1. Field of the Invention
The subject invention relates to bioelectrodes utilizing a fluid electrolyte medium. More particularly, the present invention relates to bioelectrodes which are attached at a skin surface and are utilized for applying or measuring current or potential.
2. Prior Art
The field of bioelectrodes which are attachable at a skin surface and rely on electrolyte fluids to establish electrical contact with such skin surfaces can be divided into at least two categories. The first category includes those bioelectrodes which are prepackaged with the electrolyte contained in the electrode cavity or receptacle. The second type of bioelectrode is a dry-state electrode whose receptacle is customarily filled with electrolyte immediately prior to application to a skin surface. With both types of electrodes, the user currently experiences numerous problems which make their use both inconvenient and problematic.
With respect to the prepackaged electrode, storage is a major concern. Frequently, leakage of contents from the receptacle occurs, resulting in an inoperative or defective state. Furthermore, such prefilled electrodes are difficult to apply because the protective seal which covers the electrode opening and retains the fluid within the receptacle cavity must be removed prior to application to the skin surface. After removal of this protective seal, spillage often occurs in attempting to place the electrode at the skin surface. Such spillage impairs the desired adhesive contact of the electrode to skin surface and also voids a portion of the receptacle cavity. The consequent loss of electrolyte fluid tends to disrupt electrical contact with the electrode plate contained therein and otherwise disrupts the preferred uniform potential gradient to be applied.
Although dry-state electrodes have numerous advantages in ease of storage and greater adaptability for various types of electrode applications, several problems remain. For example, the electrolyte receptacles of such electrodes are conventionally filled through their opening prior to application to the patient's skin surface. Therefore, the same problem of spillage and loss of electrolyte upon application occurs as with the prefilled electrode.
Frequently, such electrodes are not well structured to develop the proper uniform current flow required in iontophoresis applications. Such nonuniform current flow may result from improper spacial relationship between the exposed skin surface and electrode plate, as well as from the occurrence of air pockets within the receptacle cavity. This effect occurs because of the nonuniform impedance associated with such air pockets, thereby disrupting the electric field and current path established between the electrode and exposed skin surface. Such effects are particularly troublesome in iontophoresis applications, where the induction of medicaments (such as anesthetic) relies upon the amount of current flow at any given point at the skin surface. Therefore, a nonuniform current flow results in unequal distribution of anesthetic through the skin surface, along with increased risk of burns. Previous methods of filling dry-state electrodes have not attempted to remedy the disrupted influence of such air pockets within the electrode cavity or the spillage problem of conventional filling techniques.